Acquiring a non-native speech contrast is often difficult. High variability phonetic training (HVPT) is a well-established method used to train learners on non-native phoneme contrasts: it critically uses high variability (HV) input after earlier studies using low variability (LV) input had proved unsuccessful. HVPT has since been successfully applied in many different studies with adult participants, but much less so with children. The current study further investigates the effect of input variability on phonetic training for children, examining whether, like adults previously, they show a HV benefit. In a two-week training study, 58 Dutch 7-year-olds and 51 Dutch 11-year-olds were trained on Standard Southern British English vowel contrasts using either HV (multiple talkers) or LV (single talker) input. Both groups improved in training, however, contrary to the idea of a plasticity benefit for younger learners, only the 11-year-olds showed evidence of generalization i.e. improvement on pre/post-tests with unfamiliar talkers, with Bayes Factors showing null evidence for 7-year-olds. Critically, there was no evidence that 11-year-olds showed greater generalization following HV input, with evidence for the null in some tests. Results are discussed in terms of difficulties of the training and testing tasks and possible interactions with the benefits of input variability.